1. Field of the Invention
The exemplary embodiment(s) of the present invention relates to a current sensing amplifier and method thereof. More specifically, the exemplary embodiment(s) of the present invention relates to a current sensing amplifier and method thereof capable of canceling the offset voltage effect.
2. Description of Related Art
In the technical field of non-volatile memory, the data stored in the memory is read by applying current source or voltage source to the specific memory unit to generate a sensing current by transistors and to determine the logic state of such date stored in the memory by reading the sensing current.
With the evolution of semi-conductor manufacturing technology, the high-volume memory is provided by increasing the memory unit numbers on unit area. However, the offset effect due to transistor threshold voltage(Vth) may cause the result of logic state error reading owing to the random doping in the semi-conductor manufacturing process and the reducing manufacturing scale.
For the purpose of canceling the threshold voltage offset voltage, a high speed comparator with offset cancellation is disclosed by Edward Wai in US patent with U.S. Pat. No. 5,032,744. In the patent, two capacitors are used to block all DC voltage during a reset phase and a differential amplifier is driven into saturation during a regeneration phase so as to cancel the offset effect. However, the logic data determination speed may be decreased because of the charging and discharging time of the two capacitors are required.
Sensing amplifier with offset cancellation and charge-share limited swing drivers is disclosed by Esin Terzioglu due to the same purpose in US patent with U.S. Pat. No. 6,781,421. In the patent, different threshold voltage offset of different transistors are stored in a capacitor. When the data logic state is determined, the stored threshold voltage offset is added to correct the determining result. The capacitor also need to go through the charging and discharging state.